Is that not a thing in the adult world? Do it all the time in peds. Bicarb is nice because it's fizzy. 3% or even 7% hypertonic saline is useful if pulling out really thick stuff. Mucomyst nebs are useful as well. The pharmacies at my last two hospitals are stingy with the Pulmozyme, but might be worth grabbing a gram stain on the trach aspirate to see if you have WBC's that you break apart with the expensive med.
IPV is also a better choice than manual CPT to go along with your Cough Assist